The present invention is concerned with ferrous alloy composition and manufacture and coating methods of mechanical products using the ferrous alloy in order to improve wear, corrosion, and heat resistances of the mechanical products which are exposed to friction and wear environments with or without lubricating condition.
In order to improve the friction and wear resistances of the mechanical products such as the connection parts interconnecting the main body, boom, arm and bucket with each other, roller, gear and mechanical seal which subject to high surface pressure, there have been employed various techniques on the ferrous material such as carburization, nitridization, high frequency induction hardening, sulfurization, polymer coating with PTFE, electroless Ni plating, and ceramic coating.
However, in terms of the friction and wear characteristics such as mobile friction coefficient, wear amount, and wear depth, the mechanical products made by applying the conventional techniques have not exhibited the satisfactory properties, and the application of new material and manufacture techniques has been required.
For example, although the carburization increases the surface hardness, the high surface pressure acted on the mechanical parts which are subject to high friction condition pushes away the lubricant despite the use of grease lubrication, and decreases considerably the friction and wear resistances of the mechanical products. Accordingly, in case of excavator, there has been a problem that the grease should be often supplied, for instance, one to three times a day. In addition, for undercarriage roller and idler bush, the lubricants have been supplied with sealing but there have been still problems such as short wear lifetime and lubricant leakage.
In order to solve the above problems, the present inventor proposed the use of urethane rubber bushing in the Korean Utility Model Appln. No. 92-6031. However, although urethane rubber bushing improves the friction characteristics, its use has been restricted due to the durability problem for the parts which are subject to high surface pressure. Furthermore, the surface coating on the steel matrix using Al.sub.2 O.sub.3, WC, and Cr.sub.3 O.sub.2, etc., to increase the surface hardness exhibits a poor shock resistance due to the difference in physical property between matrix and coating layer, but also causes the problem of poor durability with time since the thermally transformed matrix phase formed during coating process deteriorates the mechanical properties. In fact, for the mechanical parts such as drawing die and plug which are subject to high shear sliding stress, the surfaces coated as above cannot endure the mechanical stress for long time and readily wear out, causing the problem of frequent replacement of the mechanical parts. For these reasons, the expensive die steel or WC sintered dice material have been used, but their uses have been restricted due to the wearability and expensive manufacture cost.
On the other hand, since it was disclosed by Duwez, et al in 1960 that the amorphous materials can be formed by rapidly cooling the metal melt and exhibit the improved mechanical properties compared to the crystalline materials in terms of strength, corrosion resistance, etc., the application of amorphous materials to the mechanical products has been the subject of many research works. However, In order to obtain the amorphous phase, the melt should be supercooled by 10.degree. C./see or over, which makes the processing more difficult.